Apparatus and method for introducing vaporizable materials into an electron tube envelope



Jan. 30, 1968 R, w WOLFE 3,366,820.

APPARATUS AND METHOD FOR INTRODUCING VAPORIZABLE MATERIALS INTO AN ELECTRON TUBE ENVELOPE Filed Jan. 1.5, 1965 37 22 37 i v z 36 Ii 35 0U I U U 1, g o I FIGQI INVENTOR.

ROGER w. WOLFE ATTORNEY United States Patent P 3,366,820 APPARATUS AND METHOD FOR INTRODUCING VAPORIZABLE MATERIALS INTO AN ELEC- TRON TUBE ENVELOPE Roger W. Wolfe, Plainfield, N.J., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Jan. 15, 1965, Ser. No. 425,798 12 Claims. (Cl. 313-1095) ABSTRACT OF THE DISCLOSURE heating to a temperature at which the powdered glass melts and covers the mercury amalgam. When the capsule is cooled and the molten glass solidifies, the mercury amalgam is enclosed thereby, and the free mercury in the enevelope is prevented from recombining with the amalgam.

This invention relates to the art of introducing a substance into the atmosphere within a closed container.

The principles of the invention are applicable to a wide variety of substances and containers within which they may be provided, as those skilled in the :art will appreciate. For purposes of illustration, however, the invention will be described as it relates to the introduction of mercury into the envelope of a light-producing tube, particularly a cathode glow indicator tube.

A cathode glow indicator tube of the type under consideration includes a transparent envelope which contains an anode electrode, generally a plurality of cathode glow indicator electrodes, and a gas suitable for supporting cathode glow.. Argon, neon, and the like are commonly used for this purpose. When a. suitable electrical potential is applied between the anode and a selected cathode electrode, the cathode electrode glows and current flows through the gas from the cathode to the anode. Generally, during this operation, the cathode is bombarded by positive ions which may cause erosion of the material of the cathode surface. This is known as cathode sputtering. The sputtered metal may be deposited on the dormant cathode electrodes in the tube and on the tube envelope, and, ultimately, the tube becomesunusable.

Cathode sputtering in tubes of the type under consideration has been substantially eliminated by the provision of mercury vapor in the usual gas atmosphere of argon, neon, or the like. In one method of introducing the mercury into the tube, a glass capsule containing a drop of mercury is mounted inside the tube envelope. At a selected time in the manufacture of the tube, the glass capsule is broken to free the mercury and allow it to enter the tube atmosphere. In another method, the mercury is provided in a suitable amlgam, and again at a selected time, the amalgam is heated to vaporize the mercury and cause it to enter the tube atmosphere. This method has been found to be unsatisfactory because the amalgam gradually re-absorbs the mercury from the tube atmosphere. When this occurs, cathode sputtering recurs, along with its undesirable side effects.

Accordingly, the objects of the invention concern the provision of improved apparatus and method for introducing a vaporizable substance into a container.

The objects of the invention also concern the provision of improved apparatus and method for introducing a substance into a container from an alloy or amalgam of the substance.

Still another object of the invention is to provide improved apparatus and method for introducing mercury into a container from an amalgam and preventing the amalgam from re-absorbing the mercury.

Briefly, according to the invention, the substance, for example mercury, to be introduced into a container 1s provided in alloy or amalgam form in a suitable carrier. A fusible, film-forming material having a higher melting point than the amalgam or alloy is also included in the carrier. The method of the invention comprises disposing the aforementioned carrier in the container into which the mercury is to be released, and, at a selected time, beating the alloy to vaporize the mercury. After this has been achieved, the carrier is heated to the temperature at which the fusible material melts and flows to cover and enclose the remaining amalgam. The carrier is then allowed to cool, and the fusible material solidifies and encloses and effectively immobilizes the alloy or amalgam remaining therein. Thus, the amalgam or alloy is unable to re-absorb the mercury.

The invention is described in greater detail by reference to the drawing, wherein:

FIG. 1 is a perspective view of a cold cathode gaseous glow tube embodying the invention; and

FIG. 2 is a sectional elevation view of a carrier used in practicing the invention.

As set forth above, the principles of the invention are broadly applicable to the introduction of many different types of substances into substantially any type of container. For purposes of illustrating the invention, the following description relates to the provision of mercury in a cold cathode indicator tube, for example, a type 6844A cathode glow indicator tube.

Referring to the drawings, a typical gaseous indicator glow tube 10 includes an envelope 12 which has been evacuated of air and filled with a gas suitable for supporting cold cathode glow. Such a gas may be argon, neon, or the like at a suitable pressure which may be in the range of about 50 to about mm. of Hg. The envelope includes a base portion, or stem 14, through which metal pins 16 extend and by means of which electrodes inside the tube are connected to external electrical circuit elements. Two diametrically opposed pins 16 are provided inside the envelope with extension posts 18 which are used to support various electrode elements of the tube. The posts 18 are coated with a suitable insulating material (not shown) such as glass.

The envelope 12 also includes a transparent viewing window 20, through which glowing indicator cathode electrodes 22 may be viewed. Ten cathodes 22 are usually provided in this type of tube, but only two are shown to simplify the drawing. The cathode electrodes are provided with apertured tabs (not shown), by means of which they are mounted and supported on the posts 18 with an insulating spacer 24 between each cathode. Each cathode indicator electrode is electrically connected by a lead 28 to one of the pins 16 inside the envelope 12.

The tube 10 also includes an anode electrode which is in the form of a cup 36 having a pair of diametrically opposed longitudinal slots 37 aligned with the support posts 18 and through which the cathode leads 28 extend to the pins 16. The stack of cathode electrodes is, in effect, contained within the cup. The cup rests on, but is insulated from, the pins 16 by an insulating disk 35 of mica or the like. The anode cup is also electrically connected to one of the pins 16 by a suitable lead (not shown).

As set forth above, sputtering of the metal of the cathodes 22 during operation of the tube 10 is substantially eliminated by the inclusion of mercury as a sputter-inhibiting agent within the envelope. According to the invention, the mercury is introduced as follows. A conductive carrier 40, of a form well known in the art, is provided with a quantity 4d of an amalgam of mercury. Any suitable amalgam may be employed for the purposes of the invention so long as the temperature at which it melts and releases mercury vapor is a usable temperature. One suitable amalgam includes magnesium, silicon, and mercury, and has a melting point of about 600 C. Other amalgams comprising, for example, magnesium and chlorides of mercury may also be employed in a combination having a suitable melting point. In addition, according to the invention, a quantity 48 of a fusible material, for example a powdered glass frit, is provided in the carrier disposed generally over the amalgam. The frit has a melting point higher than that of the amalgam 44, say about 750 C. If the mercury amalgam is in powder form, the glass frit may also be mixed intimately with the amalgam. The carrier 40 containing the amalgam 44 and the fusible material 48 is suitably mounted within the envelope 12 by means of a lead or tab 50 secured, for example, to a pin 16 or to the outside of the cup anode 36.

According to the method of the invention, after the tube has been assembled and properly processed to provide the desired gas atmosphere within the envelope 12, and it is desired to introduce the mercury into the envelope, the carrier 49 is heated, for example, by means of induction heating, to the temperature at which the amalgam melts, and the mercury is vaporized and escapes from a suitable aperture 60 provided in the carrier. After the mercury has been released, the carrier is heated to the higher temperature at which the glass frit melts and flows to form a film which covers the amalgam. The carrier is then allowed to cool so that the glass solidifies and provides a protective shield or coating for the amalgam. With the amalgam thus protected, it cannot reabsorb the mercury from the tube atmosphere during subsequent tube operation. For optimum results, all of the amalgam should be coated by the glass film and shielded from the mercury-containing atmosphere of the tube.

What is claimed is:

1. Material handling apparatus comprising a carrier for carrying a substance to be released into the atmosphere in a container and adapted to be mounted inside said container and exposed to the atmosphere therein,

a first quantity of material in said carrier and including the substance to be released, and

a second quantity of a film-forming material in said carrier and in intimate relation with said first quantity of material whereby when said substance is released from said first quantity of material, said filmforming material can be treated to form a film in contact with and covering said first quantity of material and shielding it from the atmosphere into which said substance has been released.

2. The apparatus defined in claim 1 wherein said first quantity of material has a characteristic first temperature at which said substance is released and said film-forming material has a characteristic second temperature at which it forms a film, said second temperature being higher than said first temperature.

.3. Material handling apparatus comprising a carrier for carrying a substance to be released into the atmosphere in a container and adapted to be mounted inside said container and exposed to the atmosphere therein,

a first quantity of material in amalgam form in said carrier and including the substance to be released, and

a second quantity of a fusible film-forming material in powder form in said carrier and in intimate contact with said first quantity of material whereby when said amalgam is heated to release said substance from said first quantity of material, said film-forming material can be heated to form a film covering said first quantity of material and shielding it from the atmosphere into which said substance has been released.

4. Material handling apparatus comprising a conductive carrier for carrying a substance to be released into the atmosphere in a container and adapted to be mounted inside said container and exposed to the atmosphere therein,

a first quantity of an amalgam in said carrier and including the substance to be released, said amalgam having a first characteristic temperature at which said substance is released,

a second quantity of a film-forming material in powder form in said carrier and in intimate relation with said first quantity of material, said second material having a temperature at which it flows which is higher than said first temperature whereby when said substance is released trom said first quantity of material at said first temperature, said film-forming material can be heated to form a film covering said first quantity of material and shielding it from the atmosphere into which said substance has been released.

5. Material handling apparatus comprising a carrier for carrying a substance to be released into the atmosphere in a container and adapted to be mounted inside said container and exposed to the atmosphere therein,

first quantity of a mercury amalgam in said carrier, a second quantity of a powdered glass frit in said carrier and in intimate relation with said amalgam whereby after the amalgam is heated to release the mercury, the glass frit can be heated and fused to form a film covering the amalgam and shielding it from the atmosphere into which the mercury has been released.

6. Apparatus having a gas atmosphere and adapted to include a vaporizable substance in said atmosphere comprising a container having an atmosphere within its confines,

and means inside said container for carrying a substance to be released into the atmosphere in said container, said means comprising a carrier for carrying a substance to be released into the atmosphere in a container,

a first quantity of material in said carrier and including the substance to be released, and

a second quantity of a film-forming material in said carrier and in operative relation with said first quantity of material whereby when said substance is released by said first quantity of material, said filmforming material can be treated to form a film covering said first quantity of material and shielding it from the atmosphere into which said substance has been released,

said carrier being adapted to be heated to cause the release of said substance and to cause the formation of said film.

7. The apparatus defined in claim 6 wherein said carrier is mounted in said container so that it can be electrically heated by a power source external to said container.

8. A cold cathode indicator tube including an envelope containing an atmosphere for supporting cathode glow,

a plurality of cathode indicator electrodes in said envelope,

an anode electrode in operative relation with said cathode electrodes, and

a carrier mounted inside said envelope for carrying a substance to be released into said gas atmosphere, said carrier containing a first quantity of material includingthe substance to be released, and a second quantity of a film-forming material in intimate relation with said first quantity of material whereby when said substance is released from said first quantity of material, said film-forming material can be treated to form a film covering said first quantity of material and shielding it from the atmosphere ito which said substance has been released.

9. The method of introducing a substance into the atmosphere of a container and retaining it in said atmosphere comprising the steps of providing in a capsule a first material including said substance to be released into the container, providing a second film-forming material in said capsule in intimate relation with said first material, mounting said capsule inside said container, releasing said substance from said first material into the atmosphere in said container, and forming in said capsule a film of said second material enclosing and in contact with said first material and shielding it from the atmosphere in said container.

10. The method of introducing a substance into the atmosphere of a container and retaining it in said atmosphere comprising the steps of providing in a carrier a first material including said substance which is to be released,

providing a second film-forming material in said carrier in intimate relation with said first material,

mounting said carrier in said container,

heating said first material to a first temperature to release said substance from said first material into the atmosphere in said container, and

heating said second material to a second higher temperature to form a film of said second material in said carrier enclosing said first material and shielding it from the atmosphere in said container.

11. The method of introducing a substance into the atmosphere of a container and retaining it in said atmosphere comprising the steps of providing an amalgam including said substance in the container into which the substance is to be released,

providing a second powdered film-forming material in said container in initimate relation with said amalheating said amalgam to release said substance into the atmosphere in said container, and

heating said second material to cause it to fuse and form a film enclosing said amalgam and shielding it from the atmosphere in said container.

12. The method of introducing a substance into the atmosphere of a container and retaining it in said atmosphere comprising the steps of providing an amalgam including mercury in the container into which mecury is to be released,

providing a powdered glass frit in said container in intimate relation with said amalgam, heating the amalgam to release the mercury into the atmosphere in said container,

heating the glass frit to cause it to fuse and form a film of said second material enclosing said first material and shielding it from the atmosphere in said container, and

cooling the container to cause the film of glass to harden.

References Cited UNITED STATES PATENTS 1,841,034 1/1932 Ives 316-20 X 2,449,493 9/ 1948 Longini 3l620 X 2,667,600 l/l954 Golf 31318l X 2,791,715 5/1957 Heins 313174X 3,275,873 9/1966 Houston 313--174 X JAMES W. LAWRENCE, Primary Examiner.

C. R. CAMPBELL, Assistant Examiner. 

